: : Nov. 27, 2000 (Washington) -- Scientists have long theorized that about: 15 different genes play a role in who is born with the severe brain disorder: autism -- and now they've finally found one of those genes.

: A study of 57 autism patients found that 40% carry a mutated version of: the HOXA1 gene, which plays a crucial role in early brain development,: University of Rochester scientists reported Monday.

: Children need to inherit just one copy of the mutated gene from one: parent to have autism. In fact, scientists found only one patient, a very: severe case, who inherited a copy of the bad gene from both parents,: suggesting that when that happens the fetus usually dies, said lead: researcher Patricia Rodier, who heads the university's National Institutes: of Health (NIH)-funded autism research center.

: The NIH called the finding a significant step in understanding what: predisposes people to developing autism. More than 400,000 Americans: have the brain disorder, characterized by profound social withdrawal,: repetitive behavior and inability to communicate. Research suggests it's: caused when something goes wrong during critical fetal brain: development -- a theory that the gene discovery, which was published in: the December issue of the journal Teratology, supports.

: Why don't parents who harbor the defective gene have autism: themselves? Some do have very subtle symptoms, suggesting that: something else, perhaps some other gene, keeps the autism-related: gene in check, Rodier said.

: HOXA1 is one of a family of genes vital to early embryo development: because genes in the group turn on or off other genes. HOXA1's specific: role is in brain development. Mice who lack this gene have brainstem: damage, malformed ears and other classic signs of autism -- one reason: Rodier's research team decided to check the gene's role in people.

: It's not the kind of gene that could ever be fixed with gene therapy. But: the discovery may help doctors unravel just how the brain changes when: HOXA1 is abnormal, Rodier said.